Unhappy with the gaps in the institutions/policy answer, some historians and political scientists have turned instead to explanations based on culture. Distinguished names in this tradition include Edward Banfield, Robert Putnam, and David Landes.

They argue that institutions and policies are not available for the photocopying from one society to the next. They emerge organically from that society's history and traditions. If a society lacks the preconditions to develop those institutions and policies, the society will not sustain them, or derive benefit from them if they are imposed from the top down.

A society that regards warriors as superior to businesspeople; a society where people recognize no obligations to anyone other than their own kin; a society in which "work" is regarded as appropriate only for slaves, never for free people; or for women, never for men—such societies won't develop (or so the culture cluster of answers holds). Institutional or policy change will do such societies no good, because the changes will be rejected like a failed organ transplant.

That sounds fatalistic, and to some degree it is. It does not have to be, for the reason propounded by Daniel Patrick Moynihan: "The central conservative truth is that it is culture, not politics, that determines the success of a society. The central liberal truth is that politics can change a culture and save it from itself." One outstanding example: Japan under the Meiji emperor. Over a generation, an authoritarian regime transformed a feudal society into an industrial economy—and opened the way for the great Japanese catch-up in the 20th century.

However, such transformations are difficult and rare. "Cultural" explanations are thus the special interest of development pessimists—and the special bane of development optimists. (See Fareed Zakaria's column, for a fine example of the interplay of these contending emotions.)

Yet the cultural cluster of answers is not without problems of its own. Where does culture come from? Why does it sometimes evolve—and sometimes not? What * is * culture anyway? Most fundamentally, isn't there a suspiciously after the fact quality to cultural explanations? Did Chinese culture—already 5,000 years old—really suddenly transform itself from anti-developmental in the 19th century to developmental in the 21st? Or is "culture" just a catch-all for "everything we can't readily understand and explain"?

Those doubts lead some thinkers—and most famously one of the thinkers admired by Mitt Romney, Jared Diamond—to look in a very different direction: toward geography and its consequences.